<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .one {
            width: 200px;
            height: 100px;
            background-color: pink;
            float: left;
        }

        .two {
            width: 200px;
            height: 100px;
            background-color: blueviolet;
            float: left;
        }

        .boxtwo {
            height: 500px;
            width: 600px;
            background-color: black;
        }

        .clear {
            clear: both;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="one">1</div>
        <div class="two">2</div>
        <!-- 额外标签法只适合于块元素 例如span不适用 -->
        <div class="clear"></div>
    </div>
    <div class="boxtwo">woshizhu</div>
</body>

</html>